text: // SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
  /******************************************************************************
   *
   * Module Name: nswalk - Functions for walking the ACPI namespace
   *
   * Copyright (C) 2000 - 2020, Intel Corp.
   *
   *****************************************************************************/
  
  #include <acpi/acpi.h>
  #include "accommon.h"
  #include "acnamesp.h"
  
  #define _COMPONENT          ACPI_NAMESPACE
  ACPI_MODULE_NAME("nswalk")
  
  /*******************************************************************************
   *
   * FUNCTION:    acpi_ns_get_next_node
   *
   * PARAMETERS:  parent_node         - Parent node whose children we are
   *                                    getting
   *              child_node          - Previous child that was found.
   *                                    The NEXT child will be returned
   *
   * RETURN:      struct acpi_namespace_node - Pointer to the NEXT child or NULL if
   *                                    none is found.
   *
   * DESCRIPTION: Return the next peer node within the namespace. If Handle
   *              is valid, Scope is ignored. Otherwise, the first node
   *              within Scope is returned.
   *
   ******************************************************************************/
  struct acpi_namespace_node *acpi_ns_get_next_node(struct acpi_namespace_node
  						  *parent_node,
  						  struct acpi_namespace_node
  						  *child_node)
  {
  	ACPI_FUNCTION_ENTRY();
  
  	if (!child_node) {
  
  		/* It's really the parent's _scope_ that we want */
  
  		return (parent_node->child);
  	}
  
  	/* Otherwise just return the next peer */
  
  	return (child_node->peer);
  }
  
  /*******************************************************************************
   *
   * FUNCTION:    acpi_ns_get_next_node_typed
   *
   * PARAMETERS:  type                - Type of node to be searched for
   *              parent_node         - Parent node whose children we are
   *                                    getting
   *              child_node          - Previous child that was found.
   *                                    The NEXT child will be returned
   *
   * RETURN:      struct acpi_namespace_node - Pointer to the NEXT child or NULL if
   *                                    none is found.
   *
   * DESCRIPTION: Return the next peer node within the namespace. If Handle
   *              is valid, Scope is ignored. Otherwise, the first node
   *              within Scope is returned.
   *
   ******************************************************************************/
  
  struct acpi_namespace_node *acpi_ns_get_next_node_typed(acpi_object_type type,
  							struct
  							acpi_namespace_node
  							*parent_node,
  							struct
  							acpi_namespace_node
  							*child_node)
  {
  	struct acpi_namespace_node *next_node = NULL;
  
  	ACPI_FUNCTION_ENTRY();
  
  	next_node = acpi_ns_get_next_node(parent_node, child_node);
  
  
  	/* If any type is OK, we are done */
  
  	if (type == ACPI_TYPE_ANY) {
  
  		/* next_node is NULL if we are at the end-of-list */
  
  		return (next_node);
  	}
  
  	/* Must search for the node -- but within this scope only */
  
  	while (next_node) {
  
  		/* If type matches, we are done */
  
  		if (next_node->type == type) {
  			return (next_node);
  		}
  
  		/* Otherwise, move on to the next peer node */
  
  		next_node = next_node->peer;
  	}
  
  	/* Not found */
  
  	return (NULL);
  }
  
  /*******************************************************************************
   *
   * FUNCTION:    acpi_ns_walk_namespace
   *
   * PARAMETERS:  type                - acpi_object_type to search for
   *              start_node          - Handle in namespace where search begins
   *              max_depth           - Depth to which search is to reach
   *              flags               - Whether to unlock the NS before invoking
   *                                    the callback routine
   *              descending_callback - Called during tree descent
   *                                    when an object of "Type" is found
   *              ascending_callback  - Called during tree ascent
   *                                    when an object of "Type" is found
   *              context             - Passed to user function(s) above
   *              return_value        - from the user_function if terminated
   *                                    early. Otherwise, returns NULL.
   * RETURNS:     Status
   *
   * DESCRIPTION: Performs a modified depth-first walk of the namespace tree,
   *              starting (and ending) at the node specified by start_handle.
   *              The callback function is called whenever a node that matches
   *              the type parameter is found. If the callback function returns
   *              a non-zero value, the search is terminated immediately and
   *              this value is returned to the caller.
   *
   *              The point of this procedure is to provide a generic namespace
   *              walk routine that can be called from multiple places to
   *              provide multiple services; the callback function(s) can be
   *              tailored to each task, whether it is a print function,
   *              a compare function, etc.
   *
   ******************************************************************************/
  
  acpi_status
  acpi_ns_walk_namespace(acpi_object_type type,
  		       acpi_handle start_node,
  		       u32 max_depth,
  		       u32 flags,
  		       acpi_walk_callback descending_callback,
  		       acpi_walk_callback ascending_callback,
  		       void *context, void **return_value)
  {
  	acpi_status status;
  	acpi_status mutex_status;
  	struct acpi_namespace_node *child_node;
  	struct acpi_namespace_node *parent_node;
  	acpi_object_type child_type;
  	u32 level;
  	u8 node_previously_visited = FALSE;
  
  	ACPI_FUNCTION_TRACE(ns_walk_namespace);
  
  	/* Special case for the namespace Root Node */
  
  	if (start_node == ACPI_ROOT_OBJECT) {
  		start_node = acpi_gbl_root_node;
  	}
  
  	/* Null child means "get first node" */
  
  	parent_node = start_node;
  	child_node = acpi_ns_get_next_node(parent_node, NULL);
  	child_type = ACPI_TYPE_ANY;
  	level = 1;
  
  	/*
  	 * Traverse the tree of nodes until we bubble back up to where we
  	 * started. When Level is zero, the loop is done because we have
  	 * bubbled up to (and passed) the original parent handle (start_entry)
  	 */
  	while (level > 0 && child_node) {
  		status = AE_OK;
  
  		/* Found next child, get the type if we are not searching for ANY */
  
  		if (type != ACPI_TYPE_ANY) {
  			child_type = child_node->type;
  		}
  
  		/*
  		 * Ignore all temporary namespace nodes (created during control
  		 * method execution) unless told otherwise. These temporary nodes
  		 * can cause a race condition because they can be deleted during
  		 * the execution of the user function (if the namespace is
  		 * unlocked before invocation of the user function.) Only the
  		 * debugger namespace dump will examine the temporary nodes.
  		 */
  		if ((child_node->flags & ANOBJ_TEMPORARY) &&
  		    !(flags & ACPI_NS_WALK_TEMP_NODES)) {
  			status = AE_CTRL_DEPTH;
  		}
  
  		/* Type must match requested type */
  
  		else if (child_type == type) {
  			/*
  			 * Found a matching node, invoke the user callback function.
  			 * Unlock the namespace if flag is set.
  			 */
  			if (flags & ACPI_NS_WALK_UNLOCK) {
  				mutex_status =
  				    acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
  				if (ACPI_FAILURE(mutex_status)) {
  					return_ACPI_STATUS(mutex_status);
  				}
  			}
  
  			/*
  			 * Invoke the user function, either descending, ascending,
  			 * or both.
  			 */
  			if (!node_previously_visited) {
  				if (descending_callback) {
  					status =
  					    descending_callback(child_node,
  								level, context,
  								return_value);
  				}
  			} else {
  				if (ascending_callback) {
  					status =
  					    ascending_callback(child_node,
  							       level, context,
  							       return_value);
  				}
  			}
  
  			if (flags & ACPI_NS_WALK_UNLOCK) {
  				mutex_status =
  				    acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
  				if (ACPI_FAILURE(mutex_status)) {
  					return_ACPI_STATUS(mutex_status);
  				}
  			}
  
  			switch (status) {
  			case AE_OK:
  			case AE_CTRL_DEPTH:
  
  				/* Just keep going */
  				break;
  
  			case AE_CTRL_TERMINATE:
  
  				/* Exit now, with OK status */
  
  				return_ACPI_STATUS(AE_OK);
  
  			default:
  
  				/* All others are valid exceptions */
  
  				return_ACPI_STATUS(status);
  			}
  		}
  
  		/*
  		 * Depth first search: Attempt to go down another level in the
  		 * namespace if we are allowed to. Don't go any further if we have
  		 * reached the caller specified maximum depth or if the user
  		 * function has specified that the maximum depth has been reached.
  		 */
  		if (!node_previously_visited &&
  		    (level < max_depth) && (status != AE_CTRL_DEPTH)) {
  			if (child_node->child) {
  
  				/* There is at least one child of this node, visit it */
  
  				level++;
  				parent_node = child_node;
  				child_node =
  				    acpi_ns_get_next_node(parent_node, NULL);
  				continue;
  			}
  		}
  
  		/* No more children, re-visit this node */
  
  		if (!node_previously_visited) {
  			node_previously_visited = TRUE;
  			continue;
  		}
  
  		/* No more children, visit peers */
  
  		child_node = acpi_ns_get_next_node(parent_node, child_node);
  		if (child_node) {
  			node_previously_visited = FALSE;
  		}
  
  		/* No peers, re-visit parent */
  
  		else {
  			/*
  			 * No more children of this node (acpi_ns_get_next_node failed), go
  			 * back upwards in the namespace tree to the node's parent.
  			 */
  			level--;
  			child_node = parent_node;
  			parent_node = parent_node->parent;
  
  			node_previously_visited = TRUE;
  		}
  	}
  
  	/* Complete walk, not terminated by user function */
  
  	return_ACPI_STATUS(AE_OK);
  }
  